XRT72L56 Datasheet, PDF (337/486 Pages) Exar Corporation – SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

áç
PRELIMINARY
XRT72L56
SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
FIGURE 139. ILLUSTRATION OF THE LOCAL RECEIVE E3 FRAMER BLOCK, TRANSMITTING AN E3 FRAME (TO THE
REMOTE TERMINAL) WITH THE “A” BIT SET TO “0”
Local Terminal
Value = 0
Transmit E3
Framer
Receive E3
Framer
A Bit
Remote
Terminal
However, if the locally computed BIP-4 value does not
match the BIP-4 value of the corresponding E3 frame,
then the Receive E3 Framer block will do the follow-
ing.
• It will inform the Remote Terminal of this fact by
having the Local Transmit E3 Framer block send the
Remote Terminal an E3 frame, with the “A” bit-field
set to “1”. This phenomenon is illustrated below in
Figure 140 and Figure 141.
Figure 140 illustrates the Local Receive E3 Framer
receiving an errored E3 frame. In this figure, the Lo-
cal Receive E3 Frame block is receiving an E3 frame
with an BIP-4 containing the value “0xA”. This value
does not match the locally computed BIP-4 value of
“0xB”. Consequently, there is an error in the previous
E3 frame.
Figure 141 illustrates the subsequent action of the
Local Transmit E3 Framer block, which will transmit
an E3 frame, with the A bit-field set to “1” to the Re-
mote Terminal. This signaling indicates that the Local
Receive E3 Framer block has received an errored E3
frame.
318